14 November 1997 Application of fiber optic distributed sensor for strain measurement in civil engineering
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We report on civil engineering applications of a fiber optic distributed strain sensor. It consists of a sensing fiber and a high performance optical time domain reflectometer (OTDR), for measuring both strain and optical loss distribution along optical fibers by accessing only one end of the fiber. The OTDR can measure distributed strain with an accuracy of better than +/- 60 X 10-6 and a high spatial resolution of up to 1 m over a 10 km long fiber. In model experiments using the OTDR, we measured the strain changes in fibers attached to the surface of a concrete test beam. The performance of the fiber strain sensor was tested by measuring the strain distribution in optical fibers and comparing the results with resistance strain gage measurements for several loads. We found that the two sets of results were similar, and in addition, we demonstrated experimentally that the sensor was able to measure an induced strain change of less than 100 by 10-6, which is nearly the elastic limit of the concrete material. These results show the potential of the OTDR to extend the application of monitoring systems to such areas as large building diagnostics for civil engineering.
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Toshio Kurashima, Tomonori Usu, Kuniaki Tanaka, Atsushi Nobiki, Masashi Sato, Kenji Nakai, "Application of fiber optic distributed sensor for strain measurement in civil engineering", Proc. SPIE 3241, Smart Materials, Structures, and Integrated Systems, (14 November 1997); doi: 10.1117/12.293504; https://doi.org/10.1117/12.293504

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